Display screen or portion thereof with a graphical user interface for messaging



FIGURE is a front view of a display screen or portion of a graphical user interface for messaging showing the new design.

Within the drawings, the dotted lines, the dot-dash lines, and the areas within the dotted or dot-dash lines show unclaimed portions of the display screen, portions of the display screen, text, or graphical elements, and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface for messaging, as shown and described. 